package com.base.dehong.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Util
{
    
    protected static char hexDigits[] =
        { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
                'e', 'f' };
        protected static MessageDigest messagedigest = null;

        static
        {
            try
            {
                messagedigest = MessageDigest.getInstance("MD5");
            }
            catch (NoSuchAlgorithmException e)
            {
                System.err.println(MD5Util.class.getName()
                        + "Init fail. MessageDigest don't support MD5Util.");
                e.printStackTrace();
            }
        }
    
    /**
     * 将字符串转成MD5值
     * 
     * @param string
     * @return
     */
    public static String stringToMD5(String string)
    {
        byte[] hash;

        try
        {
            hash = MessageDigest.getInstance("MD5").digest(
                    string.getBytes("UTF-8"));
        }
        catch (NoSuchAlgorithmException e)
        {
            e.printStackTrace();
            return null;
        }
        catch (UnsupportedEncodingException e)
        {
            e.printStackTrace();
            return null;
        }

        StringBuilder hex = new StringBuilder(hash.length * 2);
        for (byte b : hash)
        {
            if ((b & 0xFF) < 0x10)
                hex.append("0");
            hex.append(Integer.toHexString(b & 0xFF));
        }

        return hex.toString();
    }

    

    public static String getFileMD5String(File file) throws IOException
    {
        FileInputStream in = new FileInputStream(file);
        FileChannel ch = in.getChannel();
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0,
                file.length());
        messagedigest.update(byteBuffer);
        return bufferToHex(messagedigest.digest());
    }

    public static String getMD5String(String s)
    {
        return getMD5String(s.getBytes());
    }

    public static String getMD5String(byte[] bytes)
    {
        messagedigest.update(bytes);
        return bufferToHex(messagedigest.digest());
    }

    private static String bufferToHex(byte bytes[])
    {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n)
    {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++)
        {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer)
    {
        char c0 = hexDigits[(bt & 0xf0) >> 4];
        char c1 = hexDigits[bt & 0xf];
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

    public static boolean checkPassword(String password, String md5PwdStr)
    {
        String s = getMD5String(password);
        return s.equals(md5PwdStr);
    }

}
